We are going to London in September.

Just priced QF on QF and Expedia $5382 and Thai Business $6900.

I certainly would choose Thai at this price

Y on same flights with QF $2560. From what I am reading Y+ certainly does not appear to be worth over double. As I think I have said elsewhere

Leisure traveler will have little interest
Y+ curious will lose interest.
Business travel will probably use Thai or others in business after an initial period of trialling.